Synthesis and spectroscopic characterization of ternary complexes of copper(II) glycylglycine and substituted phenanthrolines

Complexes of Cu(glygly)phen {glygly =glycylglycine; phen=4,7-dimethyl [(1)], 5,6-dimethyl [(2)], 5-NO2[(3)], 5-Cl[(4)], 2-oxazolinyl (2-ox) [(5)] phenanthroline} and bis(2-oxazolinylphenanthroline)copper(II) [(6)] were synthesized and characterized by conductivity measurements, e.p.r., i.r. and reflectance electronic spectroscopies. A broad u.v.-vis. band in the 620-640 nm range and a shoulder at ca. 825 nm suggest that these complexes are five-coordinate. The e.p.r. spectra indicate a stronger equatorial ligand field in the ternary complexes which is absent in the binary Cu-phen complexes, suggesting square pyramidal coordination, whose base contains the three donor atoms from glygly (O, N, N) and one donor from the phenanthroline nitrogen atom. The other nitrogen-containing ligand of the phenanthroline is in an apical position. The spectroscopic results can be correlated with electronic and steric effects attributable to the different substituents on the phenanthroline ligands. Only small variations in the structure of the ternary complexes occur as a function of the electronic effects of substituents on the aromatic phenanthroline ring ligands. Steric hindrance predominates in determining coordination geometry around copper(II).